Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $76.96   7.332%   $82.6027   $82.60   $82.60   $82.60  
  Purchase #2 $160.58   9.395%   $175.6665   $175.67   $175.65   $175.70  
  Purchase #3 $143.34   9.672%   $157.2038   $157.20   $157.20   $157.20  
  Purchase #4 $216.99   8.303%   $235.0067   $235.01   $235.00   $235.00  
  Purchase #5 $26.30   12.627%   $29.6209   $29.62   $29.60   $29.60  
  Purchase #6 $177.45   5.259%   $186.7821   $186.78   $186.80   $186.80  
  Purchase #7 $142.60   12.331%   $160.184   $160.18   $160.20   $160.20  
  7 purchase totals = $944.22       $1,027.0667   $1,027.06   $1,027.05   $1,027.10